Common routing

ABSTRACT

A method and corresponding apparatus are provided to route a call from a customer to a destination. A call setup message sent from a customer switch intended to signal a switch to perform a call routing function or request a call routing function be performed is intercepted. A call release message sent from the switch intended to signal the customer switch of network congestion is intercepted. In response to either the call setup message or the call release message being intercepted, a routing engine is queried with the destination of the call for a specific route over which to carry the call. The call setup message is modified to include the specific route. The call release message is responded to with a re-route call message that includes the specific route. The switch is directed with either the modified call setup message or re-route call message to use the specific route to carry the call from the customer to the destination.

BACKGROUND

In Internet telephony, least cost routing is a process that providescustomers with inexpensive telephone calls. Providers offering routes todestinations are selected, evaluated, and removed based on call qualityand other measures to maintain a competitive cost base and acceptablecall quality. A provider is selected from a set of providers representedby a routing table. The routing table includes a cost of each provideroffering a route to the destination that enables least cost routing.

SUMMARY

An example embodiment of the present invention may be implemented in theform of a method or corresponding apparatus for routing a call from acustomer to a destination. The method and corresponding apparatusaccording to one embodiment of the present invention includesintercepting a call setup message sent from a customer switch to aswitch intended to signal the switch to perform a call routing functionor request a call routing function be performed. Typically, the callrouting function determines a route for the switch to use to carry thecall to the destination. Such a determined route is referred to as aswitch-determined route. The embodiment also intercepts a call releasemessage sent from the switch to the customer switch intended to signalthe customer switch of network congestion. In response to either theintercepted call setup message or the intercepted call release message,the embodiment queries a routing engine with the destination of the callfor a specific route over which to carry the call to the destination.The specific route is queried from a set of routes that is differentfrom another set of routes from which the call routing functiondetermines the switch-determined route. The embodiment modifies theintercepted call setup message to include the specific route. The callsetup message so modified is referred to as a modified call setupmessage. The embodiment responds to the call release message with are-route call message that includes the specific route. The embodimentdirects the switch with either the modified call setup message or there-route call message to use the specific route to carry the call fromthe customer to the destination.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing will be apparent from the following more particulardescription of example embodiments, as illustrated in the accompanyingdrawings in which like reference characters refer to the same partsthroughout the different views. The drawings are not necessarily toscale, emphasis instead being placed upon illustrating embodiments ofthe present invention.

FIG. 1 is a network diagram of the prior art;

FIG. 2 is a network diagram of example network in which variousembodiments may be implemented;

FIGS. 3A-3D are protocol stack diagrams;

FIG. 3E is a network diagram of an example Session Initiation Protocol(SIP) network employing some of the disclosed embodiments;

FIG. 4 is flowchart of an example process in accordance with anembodiment;

FIG. 5 is a block diagram of an example apparatus in accordance with anembodiment;

FIGS. 6A-6B are message diagrams of an example call signaling messageflow; and

FIG. 7 is block diagram of the internal structure of a computer in whichvarious embodiments may be implemented.

DETAILED DESCRIPTION

A description of example embodiments follows.

In the wholesale telephony industry, multiple providers offer routes toa destination. Which provider provides the route or otherwise takes acall, depends in part on the capacity utilization of the provider at thetime of the call. As such, the costs for calls to the same destinationcan be different. In least cost routing, the provider offering a routeto the destination at the least cost (referred to simply as the “leastcost provider”) provides the route to the destination. If the least costprovider is unable to route the call, e.g., due to insufficientcapacity, then the “next least cost provider” routes the call to thedestination. Least cost routing is enabled by routing tables thatinclude providers and their costs. However, as will be described, theserouting tables enable least cost routing to limited degree and presentother shortcomings.

FIG. 1 illustrates providers P1 through P5, 105 a-e, each providing aroute to a destination or otherwise routing a call to the destination.The providers P1 through P3, 105 a-c, are organized in a first network110 a. The providers P4 through P5, 105 d-e, are organized in a secondnetwork 110 b. The first network 110 a and second network 110 brepresent, for example, TDM networks (or other circuit-based networks),VoIP networks (or other packet-based networks) or any combinationthereof. There may be more or fewer networks. As organized, the firstnetwork 110 a is not aware of the providers P4 through P5, 105 d-e, ofthe second network 110 b. Similarly, the second network 110 b is notaware of the providers P1 through P3, 105 a-c of the first network 110a. Each network does not consider the providers of the other networkindividually. Rather the first network 110 a considers the secondnetwork 110 b, collectively, as a provider, and vice versa.

The first and second networks 110 a-b each maintain routing tables ofproviders and their costs to enable least cost routing. As noted above,the first and second networks 110 a-b each considers the other networkas a provider. This is reflected in a first routing table 115 a and asecond routing table 115 b of the first and second networks 110 a-b,respectively. Using the first routing table 115 a as an example, becausethe providers of the second network 110 b, viz., the providers P4-P5,105 d-e, are not considered, individually, but are considered,collectively, as the second network 110 b (denoted in the FIG. 1 as N2),the cost to provide a route to the destination is not the actual cost ofthe provider P4 105 d or the provider P5 105 e providing the route. Thecost may be an arbitrary value, a value configured by an operator of thefirst network 110 a or a value derived from the cost of the providersP4-P5, 105 d-e, such as an average of their costs.

In the example illustrated in FIG. 1, a call 106 from a customer 107 toa destination 108 originates in the first network 110 a. In the firstnetwork 110 a, a least cost routing process determines, according thefirst routing table 115 a, that the least cost provider of a route tothe destination 108 is the second network 110 b (having a cost of 1).The call 106 is routed over a route 111 provided by the second network110 b to the second network 110 b.

With the call 106 routed to the second network 110 b, another least costrouting process (different from the process in the first network 110 a)determines, according to the second routing table 115 b, that the leastcost provider of a route to the destination 108 is the provider P5 105 e(having a cost of 15). The call 106 is then carried from the secondnetwork 110 b over a route 112 offered by the provider P5 105 e to thedestination 108.

The cost may be an arbitrary value, a value configured by an operator ofa network or a value derived from a provider cost(s). In any case, leastcost routing using either the first or second routing table 115 a-b, isnot accurate because it does not consider the cost of the providersindividually.

Maintaining and updating separate routing tables, such as the firstrouting table 115 a and the second routing table 115 b requires moreresources, than, for example, maintaining one routing table. A networkis rarely static and undergoes frequent changes. For example, someproviders are removed while others are added. Provider costs also changeas the network topology changes. To reflect changes in the network, arouting table for the network is updated. Updating a routing tablerequires not only network and computing resources, such as bandwidth,processing cycle, and memory space, but also requires time. Separaterouting tables further increase the demand for such resources.

A call data record (CDR) is a network's account of a call. In asituation in which a call is routed over more than one network, eachnetwork accounts for only a portion of the call. Consequently, CDRs fromeach network need to be reconciled (or otherwise combined) with oneanother in order put together a complete account of the call. Referringagain to the example illustrated in FIG. 1, the call 106 originates inthe first network 110 a and is carried over the route 111 provided bythe second network 110 b to the second network 110 b. As such, in thefirst network 110 a, a first CDR of the call 106 records the secondnetwork 110 b, not the provider P5 105 e, as providing the route 111 andthe cost of the second network 110 b providing the route 111. The call106 is then carried from the second network 110 b over the route 112offered by the provider P5 105 e to the destination 108. As such, in thesecond network 110 b, a second CDR records the provider P5 105 e asproviding the route 112 to the destination 108 and the cost of theprovider P5 105 e providing the route 112.

The first and second CDRs each account for only a portion of the calland are by themselves an incomplete account of the call. A completeaccount of the call (e.g., for billing purposes) requires reconcilingthe first and second CDRs. For example, adding the cost of routing thecall 106 to the second network 110 b over the route 111 to the cost ofrouting the call 106 to the destination over the route 112. Otherarrangements between operators of each network are possible, e.g., acredit/debit arrangement. Reconciliation, however, can only occur afterthe call finishes. As such, the fact that each network has an incompleteor partial view of the call necessitates reconciling CDRs. This addscomplexity and delay.

In summary, some of the shortcomings of using separate routing tablesinclude: i) causes inaccurate least cost routing; ii) requiresadditional resources; iii) necessitates reconciling CDRs.

FIG. 2 illustrates an application server 205, in accordance with oneembodiment, routing a call 206 from a customer 207 to a destination 208.Providers P1 through P5, each offer a route 209 a-e, respectively, tothe destination 208. The routes have decreasing costs, with the route209 a offered by the provider P1 having greatest cost and the route 209e offered by the provider P5 having least cost.

The application server 205 intercepts a call setup message 210 sent froma customer switch 215 to a switch 220. Normally, the call setup message210 signals or otherwise instructs the switch 220 to perform a callrouting function or request a call routing function to be performed. Inthis way, the intercepted call setup message 210 is intended to signalthe switch 220 to perform a call routing function or request a callrouting function to be performed. In the example illustrated in FIG. 2,the call setup message 210 is sent from the customer switch 215 over apath different from the call 206, i.e., “out-of-band.” The out-of-bandcall signaling message may be, for example, any one of: Signaling SystemNumber 7 (SS7), Common Channel Signaling System 7 (CCS7), and SessionInitiation Protocol (SIP). The intercepted call setup message 210includes, for example, Initial Address Message (IAM) and Initial AddressMessage with Additional Information (IAI) from the Integrated ServicesDigital Network (ISDN) User Part (ISUP) of the SS7 set of protocols. TheIAM/IAI is sent in the “forward” direction by each switch needed tocomplete a call (or circuit) between a calling party and called partyuntil the call connects to the destination switch. The IAM/IAI containsthe called party number

Typically, the call routing function determines a route for the switch220 to use to carry the call 206 to the destination 208. Theswitch-determined route is determined from a set of routes representedby a routing table 221 (such as the first routing table 115 a of FIG.1). As described in reference to FIG. 1, the routing table 221 does notrepresent providers of another network individually. Instead, therouting table 221 represents the providers of another networkcollectively. In the example illustrated in FIG. 2, the routing table221 includes individual providers P1, P2, and P3, and their costs forproviding the routes 209 a-c, respectively, for those providers known tobe in the network to which the switch 220 belongs or otherwise resides.The routing table 221 further includes a network (denoted in FIG. 2 asN2) as a provider and a cost for using the network to provide a route tothe destination 208. Effectively, the network stands in for providers ofthat network, collectively.

According to the routing table 221, the route 209 c offered by theprovider P3 is the least cost route. This, however, is incorrect andinaccurate. The route 209 e provided by the provider P5 is the leastcost route having a cost of 1 that is less than the route 209 a having acost of 5. Because the routing table 221 does not include the providerP5, individually, but only collectively as the network N2, the leastcost route cannot be determined from the routing table 221 accurately.

The application server 205 also intercepts a call release message 245sent from the switch 220 to the customer switch 215 intended to signalthe customer switch 215 of network congestion. The call release message245 may indicate a cause or reason for a call (or circuit) beingreleased. The application server 205 may be conditioned to pass and notintercept call release messages that do not indicate network congestionas the cause. For example, the application server 205 may pass a callrelease message (denoted in FIG. 2 as 245′) to the customer switch 215that indicates that a called party line is busy or that a called party“hangs up” the call. The intercepted call release message 245 includes,for example, Release Message (REL) from ISUP of the SS7 set ofprotocols.

The application server 205, in response to intercepting either the callsetup message 210 or the call release message 245, queries a routingengine 225 for a specific route over which to carry the call 206 to thedestination 208. In one embodiment, the application server 205 queriesthe routing engine 225 with a query message or signal 230 that includesthe destination of the call. The specific route is queried from anotherset of routes represented by a common routing table 226. The set ofroutes represented by the routing table 221 and the set of routesrepresented by the common routing table 226 are different. In theexample illustrated by FIG. 2, as contrasted with the routing table 221,the common routing table 226 includes providers, individually, viz.,providers P4 and P5 and not collectively as the network N2.

As such, according to one embodiment, the application server 205 queriesfor the specific route from a set of routes that is different fromanother set of routes from which the call routing function determinesthe switch-determined route. Furthermore, the specific route and theswitch-determined route are not necessarily the same.

Unlike the routing table 221, the common routing table 226 representsproviders individually. The common routing table 226 representsproviders and their cost without being limited to a particular network.In the example illustrated in FIG. 2, the common routing table 226includes individual providers P1 through P5, and their costs forproviding the routes 209 a-c, respectively. As illustrated and accordingto one embodiment, the application server 205 queries the routing engine225 for the specific route from the set of routes represented by thecommon routing table 226. The common routing table 226 has routes inaddition to those of the other set of routes represented by the routingtable 221, viz., additional routes associated with another networkprovided by the providers P4 and P5.

According to the common routing table 226, the route 209 e offered bythe provider P5 is the least cost route. This is contrasted with theroute 209 c offered by the provider P3, the least cost route determinedaccording to the routing table 221. The route 209 e has a cost of 1 andthe route 209 a has cost of 5. 1 being less then 5, the route 209 e isthe least cost route. The route 209 a is not. Thus, least cost routeaccording to the routing table 221 is not accurate. In contrast, thecommon routing table 226 includes the providers P1 through P5, and theroutes 209 a-e that they offer, individually, and, as such, the leastcost route can be determined from the routing common routing table 226accurately.

According to another embodiment, the application server 205 re-queriesthe routing engine 225 with the destination of the call for an alternateroute over which to carry the call 206 to the destination 208 in anevent the specific route is unable to carry the call 206 to thedestination 208. In one example, in a typically least cost routingmanner, the specific route is the least cost route (i.e., being providedby the least cost provider) and the alternate route is the next leastcost route (i.e., being provided by the next least cost provider). Inthis example, the application server 205 continues to re-query forroutes having next least costs until a route is able to carry the call206 to the destination 208.

The application server 205 modifies the call setup message 210 toinclude the specific route and produces a modified call setup message240. In the example illustrated in FIG. 2, the application server 205receives the specific route in a response message or signal 235. Inanother example, the application server 205 selects the specific routefrom among several routes provided by the routing engine 225. Theapplication server 205 may receive several routes in a message similarto the response message 235.

The application server 205 responds to the call release message 245 witha re-route call message 250 that includes the specific route.

According to another embodiment, the application server 205 re-queriesthe routing engine 225 with the destination of the call for an alternateroute over which to carry the call 206 to the destination 208 in anevent the specific route is unable to carry the call 206 to thedestination 208. In event there is no alternate route (e.g., all routesprovided by the routing engine 225 have been exhausted), the applicationserver 205 passes the call release message 245 to the customer switch215.

The application server 205 directs the switch 220 to use the specificroute to carry the call 206 to the destination 208 with either themodified call setup message 240 of the re-route call message 250.

In another embodiment, the application server 205 intercepts the callsetup message 210 and the call release message 245 sent to and from theswitch 220 operating in a first network. The application server 205queries the routing engine 225 operating in a second network. Theapplication server 205 directs the switch 220 with either the modifiedcall setup message 240 of the re-route call message 250 to use thespecific route to carry the call 206 from the customer 207 to thedestination 208 located in a third network.

In this embodiment, the first, second, and third networks are different.It may be convenient to refer to the first, second, and third networksas an originating network, routing network, and destination network,respectively.

For example, in a convenient embodiment, the application server 205intercepts the call setup message 210 and the call release message 245sent to and from the switch 220 operating in a time-division multiplexed(TDM) network. The application server 205 queries the routing engine 225operating in an Internet Protocol (IP) network. The application server205 directs the switch 220 with either the modified call setup message240 of the re-route call message 250 to use the specific route to carrythe call 206 from the customer 207 to the destination 208 located inanother TDM network. In this embodiment and others, the networks mayinclude additional network elements to which the application server 205is communicatively coupled. For example, in the TDM network (such as aPublic Switched Telephone Network (PSTN)), the customer switch 215 andswitch 220 are internetworked by one or more service transfer points(STP). In the example, the application server 205 is in communicationwith the STP. In the IP network, the application server 205 and routingengine 225 are internetworked by one or more gateways, routers or otherrouting and forwarding network elements.

The foregoing examples are not intended to limit the inventive conceptsdisclosed herein. For example, the customer switch 215 and switch 220may operate in a SIP network having additional SIP network elements,such as a SIP proxy server, SIP registrar, and SIP redirect server. Inthis example, the application server 205 is in communications with oneor more of these SIP network elements. The application server 205intercepts a SIP signaling message from the customer switch 215 anddirects the switch 220 with a modified SIP signaling message.

The destination may be identified in the call setup message 210 as adialed number. The application server 205, according to one embodiment,appends a prefix to the dialed number. The appended prefix indicates thespecific route to carry the call 206 from the customer 207 to thedestination 208. The application server 205 directs the switch 220 touse the specific route indicated by the prefix that is appended to thedialed number.

In another embodiment, given a call signaling message that indicates orotherwise includes a duration of the call (or call duration), theapplication server 205 determines a cost for carrying the call 206 fromthe customer 207 to the destination 208 over the specific route as afunction of the call duration and a rate for using the specific route.Such a call signaling message includes, for example, Answer Message(ANM) from ISUP of the SS7 set of protocols. The ANM initiates billing.

The application server 205 reports the cost in a Call Detail Record(CDR). Because the specific route used to carry the call is based on thecommon routing table 226 and the scope of the table is not limited to aparticular network, the resulting CDR for the call 206 is a completeaccount of the call. As such, there are no partial accounts of the callto be reconciled. For example, in reference to FIG. 1, rather thanreconciling the first CDR that accounts, partially, for the route beingprovided by the second network 110 b with the second CDR that accounts,partially, for the route being provided by the provider P5 105 e, asingle CDR accounts for the route being provided by the provider P5 105e, completely.

Various embodiments described above enable selecting a provider from ofa common routing table, referred to herein as “common routing,” andaddress some or all of the shortcomings noted earlier. For example, oneembodiment improves the accuracy of least cost routing over othertechniques using separate routing tables by considering the cost ofproviders, individually and independent of network. Another embodiment(or the same embodiment) eliminates the need for additional resources tomaintain and update separate routing tables by using a common routingtable having a scope not limited to a particular network. For example,updating separate routing tables across networks requires the exchangeof routing update messages and time for the networks to converge withthe routing tables consistent with one another. The common routing tabledoes not require the exchange of routing update messages or time for thenetworks to converge. Yet another embodiment (or the same embodiment)eliminates the need to reconcile CDRs and reduces complexity by using acommon routing table having a scope not limited to a particular network.

Where there are multiple providers capable of providing a route orotherwise completing a call, the selection of a particular provider maybe based on one or more considerations including the cost of completingthe call through the provider (e.g., least cost routing), the quality ofservice offered by the provider, or other considerations. The providermay be selected from among others according to business rules including,for example, an agreed upon volume or percentage of traffic to becompleted through a provider in a geographic region. For instance, theremay be an agreement between a system operator (or wholesaler) and theprovider that calls for the system operator to make minimumdaily/monthly/yearly payments to a provider in exchange for the providerproviding a predetermined number of minutes of service. In thosecircumstances, the system operator would want to make sure that theprovider is used to place calls for at least the predetermined number ofminutes each day/month/year before routing calls to other provider toensure that the system operator derives the maximum amount of servicefrom the provider in exchange for the minimum guaranteed payment.Business rules taking onto account these and other similar types ofconsiderations can then be used to determine which provider to selectand use.

Business rules can and do vary from network to network, as is the casewith networks belonging to different wholesalers. Common routing enablesdisparate business rules to be unified under a common set of rules. Thisis especially useful to a wholesaler acquiring or merging networks withanother wholesaler.

Returning to FIG. 2, the customer switch 215 and the switch 220 signalone another according to a protocol. In the context of the describedembodiments, a protocol is a set of rules for networks elements, such asthe customer switch 215 and switch 220, to communicate and interact withone another. A protocol is set forth in a standard by an organization,such as the Internet Engineering Task Force (IETF) and the InternationalTelecommunication Union (ITU).

The application server 205, according to one embodiment, behaves in amanner substantially similar to the switch 220 being signaled by thecustomer switch 215 according to the protocol. The application server205 intercepts the call setup message 210, transparently, and thecustomer switch 215 is unaware that the call setup message 210 is beingintercepted. Further, the application server 205 behaves in a mannersubstantially similar to the customer switch 215 signaling the switch220 according to the protocol. The application server 205 intercepts thecall release message 245, transparently, and the switch 220 is unawarethat the call release message 245 is being intercepted.

The application server 205 directs the switch 220, transparently, andthe switch 220 is unaware of being directed by either the modified callsetup message 240 or the re-route call message 250. For example, theapplication server 205 behaves in a manner substantially similar to thecustomer switch 215 and to the switch 220 by communicating andinteracting with the customer switch 215 and switch 220 in accordancewith the set of rules defined by the protocol. The application server205 may copy all or some portion of communications between the customerswitch 215 and switch 220, for example, copying a source point code (oraddress) and/or a destination point code (or address). The applicationserver 205 may modify all or some portion of communications between thecustomer switch 215 and switch 220, for example, modifying a checksumused to check the integrity of the communications.

In some networks, communications between the customer switch 215 andswitch 220 involve additional network elements, as described above. Forexample, in a time-division multiplexed (TDM) network (or othercircuit-based network), the customer switch 215 and switch 220 (alsoknown as services switch points (SSPs)) are internetworked by one ormore service transfer points (STPs). In this example, the applicationserver 205 behaves similar to the switch 220 being signaled by thecustomer switch 215 and similar to the customer switch 215 signaling theswitch 220 by acting like an STP.

FIG. 3A illustrates a customer switch protocol stack 305, STP protocolstack 310, and switch protocol stack 315. In this context, a protocolstack is a group or suite of software elements, each itself defined by aprotocol, that interact or communicate with each other in conformancewith a networking protocol to which they collectively relate. A customerswitch (such as the customer switch 215 of FIG. 2) having the customerswitch protocol stack 305 and a switch (such as the switch 220 of FIG.2) having the switch protocol stack 315 are able to communicate with oneanother because the protocol stacks are the same.

The customer switch protocol stack 305 and the switch protocol stack 315can be divided into lower protocol layers 320 (viz., Message TransferPart Level 1 (MTP-1), Message Transfer Part Level 2 (MTP-2), and MessageTransfer Part Level 1 (MTP-3)) and an upper protocol layer 325 (viz.,Integrated Services Digital Network (ISDN) User Part (ISUP)). Incontrast, the STP protocol stack 310 only includes the lower protocollayers 320 because the function of an STP is limited to internetworkingthe customer switch 215 to the switch 220 at these layers. An STP cannotread or otherwise access information or data transported in the upperprotocol layer 325 nor is an STP concerned with such information. Thisis referred to as encapsulation in which logically separate functions ina network are abstracted from their underlying structures by inclusionor information hiding within higher level objects.

FIG. 3B illustrates the customer switch protocol stack 305 and theswitch protocol stack 315 of FIG. 3A, and an application server protocolstack 330. The application server protocol stack 330 adds functionalityto an application server (such as the application server 205 of FIG. 2)not found in a typical STP.

The application server protocol stack 330 includes a new protocol layer335 above the lower protocol layers 320 that enables an applicationserver (such as the application server 205 of FIG. 2) to read and modifyISUP messages, and direct a switch with modified ISUP messages. Forexample, an ISUP message communicated between the customer switch andswitch includes a destination of a call in the form of a dialed number.The application server reads the ISUP message communicated from thecustomer switch and queries a routing engine (such as the routing engine225 of FIG. 2) with the dialed number for a specific route, as describedabove in reference to FIG. 2. In contrast, an STP cannot read the ISUPmessage, and thus, does not know the dialed number. The applicationserver modifies the ISUP message with the specific route (e.g., byappending a prefix to the dialed number) and directs the switch with themodified ISUP message, as described above in reference to FIG. 2.

The customer switch and switch, however, are not aware of the foregoing.The application server reading and modifying ISUP messages, anddirecting a switch with modified ISUP messages is transparent to thecustomer switch and switch.

FIGS. 3C and 3D illustrate alternative application server protocolstacks 340 and 345, respectively. To intercept a call setup message orto direct a switch transparently, as described in reference to FIG. 2, aconvenient embodiment may be implemented in accordance to one of theillustrated application server protocol stacks 340 and 345.

The foregoing is but one example. The inventive concepts describedthroughout this disclosure are not intended to be limited by theexample. In another example, FIG. 3E illustrates an example SessionInitiation Protocol (SIP) network 360 employing some of the disclosedembodiments.

In FIG. 4, an example process 400 for routing a call from a customer toa destination is executed by an application server, such as theapplication server 205 of FIG. 2. The process 400 starts (401).

The process 400 intercepts (405) a call setup message (such as the callsetup message 210 of FIG. 2) sent from a customer switch (such as thecustomer switch 215 of FIG. 2) to a switch (such as the switch 220 ofFIG. 2) intended to signal the switch to perform a call routingfunction. The call setup message may request a call routing function beperformed. The call routing function determines a route for the switchto use to carry the call to the destination. The route so determined isreferred to as a switch-determined route.

The process 400 also intercepts (410) a call release message (such asthe call release message 245 of FIG. 2) sent from the switch to thecustomer switch intended to signal the customer switch to release thecall.

In response to intercepting either the call setup message or the callrelease message, the process 400 queries (415) a routing engine (such asthe routing engine 225 of FIG. 2) with the destination of the call for aspecific route over which to carry the call to the destination. Thespecific route is queried from a set of routes (such as the setrepresented by the common routing table 226 of FIG. 2) that is differentfrom another set of routes (such as the set represented by the routingtable 221 of FIG. 2) from which the call routing function determines theswitch-determined route.

The process 400 modifies (420) the call setup message that isintercepted to include the specific route. The call setup message somodified is referred to as a modified call setup message (such as themodified call setup message 240 of FIG. 2).

The process 400 responds (425) to the call release message with are-route call message (such as the re-route call message 250 of FIG. 2)that includes the specific route.

The process 400 directs (430) the switch with either the modified callsetup message of the re-route call message to use the specific route tocarry the call from the customer to the destination.

The process ends 431 with the call routed from the customer to thedestination.

FIG. 5 illustrates an example application server 500 (such as theapplication server 205 of FIG. 2) to route a call 501 from a customer502 to a destination 503. The application server 500 includes anintercepting unit/module 505, querying unit/module 510, modifyingunit/module 515, responding unit/module 520, and directing unit/module525, each communicatively coupled from one to another.

The intercepting unit/module 505 intercepts a call setup message 507sent from a customer switch 508 to a switch 509. The intercepted callsetup message 507 is intended to signal the switch 509 to perform a callrouting function or to request a call routing function be performed. Theintercepting unit/module 505 also intercepts a call release message 545sent from the switch 509 to the customer switch 508. The interceptedcall release message 545 is intended to signal the customer switch 508to release the call.

In one example, the call setup message 507 and the call release message545 are sent to and from the switch 509 operating in a time-divisionmultiplexed (TDM) network. To intercept such messages, the interceptingunit/module 505 is configured to be networked with and to receivemessages (or signals) from the TDM network. For example, theintercepting unit/module 505 is adapted with a corresponding orcompatible physical and/or logical interface(s).

Typically, the call routing function determines a route for the switch509 to use to carry the call 501 to the destination 503. The route sodetermined is referred to as a switch-determined route.

The querying unit/module 510 queries, e.g., with a query message 511, arouting engine 512 with the destination of the call for a specific routeover which to carry the call 501 to the destination 503. In one example,the application server 500 queries the routing engine 512 operating inan Internet Protocol (IP) network. To query the routing engine 512operating in such a network, the querying unit/module 510 is configuredto be networked with and to receive messages (or signals) from the IPnetwork. For example, the querying unit/module 510 is adapted with acorresponding or compatible physical and/or logical interface(s).

The specific route is queried from a set of routes that is differentfrom another set of routes from which the call routing functiondetermines the switch-determined route. The specific route iscommunicated to the application server 500, for example, in a responsemessage 513. In a convenient embodiment, the querying unit/module 510includes a sub-module to select the specific route from among routesprovided by the routing engine (e.g., returned in the response message513) in response to the querying.

The modifying unit/module 515 modifies the intercepted call setupmessage 507 to include the specific route. The call setup message 507 somodified is referred to as a modified call setup message 517.

The responding unit/module 520 responds to the call release message 545with a re-route call message 550 that includes the specific route

The directing unit/module 520 directs the switch 509 with either themodified call setup message 517 or the re-route call message 550 to usethe specific route to carry the call 501 from the customer 502 to thedestination 503.

Optionally, the application server 500 also includes a determiningunit/module 530 and reporting unit/module 535. The determiningunit/module 530 is communicatively coupled the intercepting unit/module505 described above. The reporting unit/module 535 is communicativelycoupled to the determining unit/module 530. The determining unit/module530 determines a cost for carrying the call 501 from the customer 502 tothe destination 503 over the specific route. The determining unit/module530 determines the cost as a function of a rate for using the specificroute and a call duration indicated (e.g., from start and stop times ofthe call) in an intercepted call signaling message (such as the callsetup message 507). The reporting unit/module 535 reports the cost in aCall Detail Record (CDR) 536. The CDR 536 may be used for billingpurposes. The reporting unit/module 535 reports the CDR 536 in a formatintended to be read or otherwise processed by a billing system 540.Generally, the application server 500 may be configured to communicateor network with the billing system 550.

Alternatively, application server 500 may be a general purpose computerhaving a processor, memory, communication interface, etc (described ingreater detail in reference to FIG. 6). The general purpose computer istransformed into the application server 500 and its components, forexample, by loading instructions into the processor that cause thecomputer to intercept a call setup message sent from a customer switchintended to signal a switch, intercept a call setup message from theswitch intended to signal the customer switch to release the call, querya routing engine for a specific route over which to carry the call tothe destination, modify the call setup message that is intercepted toinclude the specific route, respond to the call release message that isintercepted with a re-route call message that includes the specificroute, and direct the switch with either the modified call setup messageor the re-route call message to use the specific route to carry the callfrom the customer to the destination.

FIGS. 6A and 6B illustrate routing a call from a customer to adestination, as described above, in the context of an example callsignaling message flow. Certain elements of the example network shown inFIG. 2 are illustrated at the top of the figures (viz., the applicationserver 205, customer switch 215, and switch 220, and the routing engine225). Below is a sequence of call signaling messages to setup and torelease the call that are exchanged between the elements. Also includedare messages related to routing the call from the customer to thedestination as described above. In this example, the call signalingmessages being exchanged are from ISUP of the SS7 set of protocols.

The customer makes the call to the destination resulting in the customerswitch 215 sending an Initial Address Message (IAM) (or a call setupmessage).

At 602, the application server 205 intercepts the IAM sent from thecustomer switch 215.

At 604, the application server 205 queries the routing engine 225 on howto route the call.

At 606, the routing engine 225 responds to the application server 205with one or more routes (or providers of routes).

At 608, the application server 205 modifies the IAM to include a firstroute provided by the routing engine 205 resulting in a modified IAM,and forwards the modified IAM to the switch 220.

In the illustrated example, the first route is not available because fornetwork congestion (denoted in FIG. 6A as “No Circuit”).

At 610, the application server 205 intercepts a Release Message (REL)(or a call release message) sent from the switch 220 indicating “nocircuit available.”

At 612, the application server 205 responds with a Release CompleteMessage (RLC) to complete the release of a portion of the call towardthe switch 220.

At 614, the application server 205 generates a re-route Call DetailRecord (CDR) for the call indicating that the call is being re-routed.In FIG. 6A, the re-route CDR generated by the application server 205 isillustrated as being sent to a CDR server (or other network elementtasked with processing CDRs).

At 616, the application server 205 modifies the IAM originally sent fromthe customer switch 215 to include a second route if provided by therouting engine 205 resulting in a modified IAM. The application server205 forwards the modified IAM to the switch 220.

At 618, the switch 220 sends the modified IAM to the provider of theroute queried or otherwise selected by the application server 205.

At 620, the switch 220 receives an Address Complete Message (ACM)indicating that the call has been delivered to the destination (orfar-end).

At 622, the application server 205 intercepts the ACM forwarded by theswitch 220.

At 624, the application server 205 records the time of receiving the ACMand forwards the ACM to the customer switch 215.

At 626, the switch 220 receives an Answer Message (ANM) indicating thatthe destination answered the call.

At 628, the application server 205 intercepts the ANM forwarded by theswitch 220.

At 630, the application server 205 records the time of receiving the ANMto calculate a duration of the call (or a call duration) and forwardsthe ANM to the customer switch 215.

The call is connected end-to-end, i.e., from the customer to thedestination, and the parties talk to each other (denoted in FIG. 6B as“Call in Conversation”).

At 632, the switch 220 receives a REL indicating that the destinationhung up the call.

At 634, the application server 205 intercepts the REL forwarded by theswitch 220.

At 636, the application server 205 records the time of receiving the RELto calculate the duration of the call and forwards the REL to thecustomer switch 215.

At 638, the application server 205 generates a final CDR including thecalculated call duration. In FIG. 6B, the final CDR generated by theapplication server 205 is illustrated as being sent to the CDR server(or other network element tasked with processing CDRs).

At 640, the application server 205 intercepts a RLC sent from customerswitch 215.

At 642, the application server 205 forwards the RLC to the switch 220.

At 644, the switch 220 sends the RLC to the provider of the route andthe call is released completely.

FIG. 7 is a block diagram of the internal structure of a computer 750 inwhich various embodiments of the present invention may be implemented.The computer 750 contains system bus 779, where a bus is a set ofhardware lines used for data transfer among the components of a computeror processing system. Bus 779 is essentially a shared conduit thatconnects different elements of a computer system (e.g., processor, diskstorage, memory, input/output ports, network ports, etc.) that enablesthe transfer of information between the elements. Attached to system bus779 is I/O device interface 782 for connecting various input and outputdevices (e.g., keyboard, mouse, displays, printers, speakers, etc.) tothe computer 750. Network interface 786 allows the computer 750 toconnect to various other devices attached to a network. Memory 790provides volatile storage for computer software instructions 792 (e.g.,instructions for the process 400 of FIG. 4 for routing a call from acustomer to a destination) and data 794 used to implement an embodimentof the present invention. Disk storage 795 provides non-volatile storagefor computer software instructions 792 and data 794 used to implement anembodiment of the present invention. Central processor unit 784 is alsoattached to system bus 779 and provides for the execution of computerinstructions.

In one embodiment, the processor routines 792 (e.g., instructions forthe process 400 of FIG. 4 for routing a call from a customer to adestination) and data 794 are a computer program product (generallyreferenced 792), including a computer readable medium (e.g., a removablestorage medium such as one or more DVD-ROM's, CD-ROM's, diskettes,tapes, etc.) that provides at least a portion of the softwareinstructions for the inventive system. Computer program product 792 canbe installed by any suitable software installation procedure, as is wellknown in the art.

In another embodiment, at least a portion of the software instructionsmay also be downloaded over a cable, communication and/or wirelessconnection.

Further, the present invention may be implemented in a variety ofcomputer architectures. The computer of FIG. 7 is for purposes ofillustration and not limitation of the present invention.

While example embodiments have been particularly shown and described, itwill be understood by those skilled in the art that various changes inform and details may be made therein without departing from the scopeencompassed by the appended claims.

It should be understood that the block, flow, and network diagrams mayinclude more or fewer elements, be arranged differently, or berepresented differently. It should be understood that implementation maydictate the block, flow, and network diagrams and the number of block,flow, and network diagrams illustrating the execution of embodiments ofthe invention.

It should be understood that elements of the block, flow, and networkdiagrams described above may be implemented in software, hardware, orfirmware. In addition, the elements of the block, flow, and networkdiagrams described above may be combined or divided in any manner insoftware, hardware, or firmware. If implemented in software, thesoftware may be written in any language that can support the embodimentsdisclosed herein. The software may be stored on any form of computerreadable medium, such as random access memory (RAM), read only memory(ROM), compact disk read only memory (CD-ROM), and so forth. Inoperation, a general purpose or application specific processor loads andexecutes the software in a manner well understood in the art.

While this invention has been particularly shown and described withreferences to example embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the scope of the inventionencompassed by the appended claims.

What is claimed is:
 1. A method for routing a call from a customer to adestination, the method comprising: at an application server:intercepting a call setup message sent from a customer switch to aswitch intended to signal the switch to perform a call routing functionor request a call routing function be performed, the call routingfunction determines a route for the switch to use to carry the call tothe destination, the route so determined is a switch-determined route;intercepting a call release message sent from the switch to the customerswitch intended to signal the customer switch of network congestionassociated with the switch-determined route; in response to either thecall setup message or the call release message being intercepted,querying a routing engine with the destination of the call for aspecific route over which to carry the call to the destination, thespecific route is queried from a set of routes that is different fromanother set of routes from which the call routing function determinesthe switch-determined route; modifying the call setup message to includethe specific route, the call setup message so modified is a modifiedcall setup message; responding to the call release message with are-route call message that includes the specific route; directing theswitch with either the modified call setup message or re-route callmessage to use the specific route to carry the call from the customer tothe destination; wherein the application server performs the methodwithout needing a service transfer point 1) to intercept the call setupmessage and the call release message and 2) to direct the switch witheither the modified call setup message or re-route call message.
 2. Themethod of claim 1 wherein the customer switch and switch signal eachother according to a protocol; wherein intercepting the call setupmessage includes behaving in a manner similar to the switch beingsignaled by the customer switch to setup the call according to theprotocol, the intercepting is transparent to the customer switch, andthe customer switch is unaware that the call setup message is beingintercepted; wherein intercepting the call release message includesbehaving in a manner similar to the customer switch being signaled bythe switch to release the call according to the protocol, theintercepting is transparent to the switch, and the switch is unawarethat the call release message is being intercepted; wherein directingincludes behaving in a manner similar to the customer switch signalingthe switch according to the protocol, the directing is transparent tothe switch, and the switch is unaware of being directed by either themodified call setup message or the re-route call message.
 3. The methodof claim 1 wherein intercepting the call setup message and interceptingthe call release message includes intercepting the messages sent to andfrom the switch that operates in a time-division multiplexed (TDM)network; wherein querying includes querying the routing engine thatoperates in an Internet Protocol (IP) network; and wherein directingincludes directing the switch with either the modified call setupmessage or the re-route call message to use the specific route to carrythe call from the customer to the destination located in another TDMnetwork.
 4. The method of claim 1 wherein intercepting the call setupmessage and intercepting the call release message includes interceptingthe messages to and from the switch that operates in a first network;wherein querying includes querying the routing engine that operates in asecond network; and wherein directing includes directing the switch witheither the modified call setup message or the re-route call message touse the specific route to carry the call from the customer to thedestination located in a third network.
 5. The method of claim 1 whereinintercepting the call setup message and intercepting the call releasemessage includes intercepting an out-of-band call signaling message, anyone of: Signaling System Number 7 (SS7), Common Channel Signaling System7 (CCS7), and Session Initiation Protocol (SIP).
 6. The method of claim1 wherein querying includes querying the routing engine for the specificroute from the set of routes having routes in addition to those of theother set of routes.
 7. The method of claim 1 wherein querying includesre-querying the routing engine with the destination of the call for analternate route over which to carry the call to the destination, in anevent the specific route is unable to carry the call to the destination.8. The method of claim 7 further comprising in an event there is noalternate route, passing the call release message to the customerswitch.
 9. The method of claim 1 wherein querying includes selecting thespecific route from among routes provided by the routing engine inresponse to the querying.
 10. The method of claim 1 wherein thedestination is identified in the call setup message as a dialed number;and wherein modifying includes appending a prefix to the dialed number,the prefix indicates the specific route to carry the call from thecustomer to the destination; and directing includes directing the switchto use the specific route indicated by the prefix that is appended tothe dialed number.
 11. The method of claim 1 further comprising: givenan intercepted call signaling message that indicates a call duration,determining a cost for carrying the call from the customer to thedestination over the specific route as a function of the call durationand a rate for using the specific route; and reporting the cost in aCall Detail Record (CDR).
 12. An apparatus to route a call from acustomer to a destination, the apparatus comprising: an interceptingmodule to intercept: i) a call setup message from a customer switch to aswitch intended to signal the switch to perform a call routing functionor request a call routing function be performed, the call routingfunction determines a route for the switch to use to carry the call tothe destination, the route so determined is a switch-determined route,and ii) a call release message sent from the switch to the customerswitch intended to signal the customer switch of network congestionassociated with the switch-determined route; a querying modulecommunicatively coupled to the intercepting module to query a routingengine with the destination of the call for a specific route over whichto carry the call to the destination, the specific route is queried froma set of routes that is different from another set of routes from whichthe call routing function determines the switch-determined route; amodifying module communicatively coupled to the querying module tomodify the call setup message to include the specific route, the callsetup message so modified is a modified call setup message; a respondingmodule communicatively coupled to the querying module to respond to thecall release message with a re-route call message that includes thespecific route; a directing module communicatively coupled to themodifying module and the responding module to direct the switch witheither the modified call setup message or re-route call message to usethe specific route to carry the call from the customer to thedestination; wherein the intercepting module and the directing moduleare configured to operate without needing a service transfer point 1) tointercept the call setup message and the call release message and 2) todirect the switch with either the modified call setup message orre-route call message.
 13. The apparatus of claim 12 wherein thecustomer switch and switch signal each other according to a protocol;wherein the intercepting module is configured: i) to behave in a mannersimilar to the switch being signaled by the customer switch according tothe protocol, the intercepting module is transparent to the customerswitch, and the customer switch is unaware that the call setup messageis being intercepted, and ii) to behave in a manner similar to thecustomer switch being signaled by the switch to release the callaccording to the protocol, the intercepting module is transparent to theswitch, and the switch is unaware that the call release message is beingintercepted; and wherein the directing module is configured to behave ina manner similar to the customer switch signaling the switch accordingto the protocol, the directing module is transparent to the switch, andthe switch is unaware of being directed by either the modified callsetup message or the re-route call message.
 14. The apparatus of claim12 wherein the intercepting module includes an interface adapted tointercept the call setup and call release messages sent to and from theswitch that operates in a time-division multiplexed (TDM) networkwherein the querying module includes an interface adapted to query therouting engine that operates in an Internet Protocol (IP) network; andwherein the directing module includes an interface adapted to direct theswitch with either the modified call setup message or the re-route callmessage to use the specific route to carry the call from the customer tothe destination located in another TDM network.
 15. The apparatus ofclaim 12 wherein the intercepting module includes an interface adaptedto intercept the call setup and call release messages sent to and fromthe switch that operates in a first network; wherein the querying moduleincludes an interface adapted to query the routing engine that operatesin a second network; and wherein the directing module includes aninterface adapted to direct the switch with either the modified callsetup message or the re-route call message to use the specific route tocarry the call from the customer to the destination located in a thirdnetwork.
 16. The apparatus of claim 12 wherein the intercepting moduleincludes an interface adapted to intercept an out-of-band call signalingmessage, any one of: Signaling System Number 7 (SS7), Common ChannelSignaling System 7 (CCS7), and Session Initiation Protocol (SIP). 17.The apparatus of claim 12 wherein the querying module is configured toquery for the specific route from the set of routes having routes inaddition to those of the other set of routes.
 18. The apparatus of claim12 wherein the querying module is configured to re-query the routingengine with the destination of the call for an alternate route overwhich to carry the call to the destination in an event the specificroute is unable to carry the call to the destination.
 19. The apparatusof claim 18 wherein the intercepting module is configured to pass thecall release message to the customer switch in an event there is noalternate route.
 20. The apparatus of claim 12 wherein the queryingmodule includes a selecting sub-module to select the specific route fromamong routes provided by the routing engine in response to the querying.21. The apparatus of claim 12 wherein the destination is identified inthe call setup message as a dialed number; wherein the modifying moduleis configured to appending a prefix to the dialed number, the prefixindicates the specific route to carry the call from the customer to thedestination; and wherein the directing module is configured to directthe switch to use the specific route indicated by the prefix that isappended to the dialed number.
 22. The apparatus of claim 12 furthercomprising: a determining module communicatively coupled to theintercepting module to determine, given an intercepted call signalingmessages that indicates a call duration, a cost for carrying the callfrom the customer to the destination over the specific route as afunction of the call duration and a rate for using the specific route;and a reporting module communicatively coupled to the determining moduleto report the cost in a Call Detail Record (CDR).
 23. A non-transitorycomputer readable medium having a computer readable program thereon,wherein the computer readable program when executed on an applicationserver causes the application server to perform the steps of: intercepta call setup message sent from a customer switch to a switch intended tosignal the switch to perform a call routing function or request a callrouting function be performed, the call routing function determines aroute for the switch to use to carry the call to the destination, theroute so determined is a switch-determined route; intercept a callrelease message sent from the switch to the customer switch intended tosignal the customer switch of network congestion associated with theswitch-determined route; in response to either the call setup message orthe call release message being intercepted, query a routing engine withthe destination of the call for a specific route over which to carry thecall to the destination, the specific route is queried from a set ofroutes that is different from another set of routes from which the callrouting function determines the switch-determined route; modify the callsetup message to include the specific route, the call setup message somodified is a modified call setup message; respond to the call releasemessage with a re-route call message that includes the specific route;and direct the switch with either the modified call setup message orre-route call message to use the specific route to carry the call fromthe customer to the destination; the application server performing thesteps without needing a service transfer point 1) to intercept the callsetup message and the call release message and 2) to direct the switchwith either the modified call setup message or re-route call message.